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United States Patent |
5,230,776
|
Andersson
,   et al.
|
July 27, 1993
|
Paper machine for manufacturing a soft crepe paper web
Abstract
A paper machine for manufacturing a soft crepe paper web, comprising a wet
end (1) having a forming wire (4) for forming and carrying a paper web
(7), and a drying section (2) provided with a drying cylinder (12), said
paper machine having a first operating arrangement for manufacturing a
soft crepe paper web with certain bulk and softness values, in which first
operating arrangement the drying section has a felt (13) arranged to run
in a loop from a pick-up roll (14) at the transition between the wet end
and drying section, to a press roll (15) at the drying cylinder, and the
carrying forming wire runs up to the pick-up roll (14) to transfer the
paper web to the felt (13). According to the invention the paper machine
is rebuildable between said first operating arrangement and a second
operating arrangement for the production of a soft crepe paper web having
higher bulk and softness values in relation to the first operating
arrangement and in which second operating arrangement the carrying forming
wire (4a) runs up to the press roll (15). Said felt is replaced by a belt
(25) of wire type, movable in a loop from the pick-up roll (14) to the
press roll in contact with the carrying forming wire (4a), while enclosing
the paper web therebetween in order to form a sandwich structure. Means
(29-31) producing jets of air are arranged along the sandwich structure to
remove water from the paper web (7). Further cleaning means (33-36, 38)
are disposed along the belt (25) to clean it so that the permeability to
water and air is maintained.
Inventors:
|
Andersson; Ingmar A. (Hammaro, SE);
Hellner; Cai O. (Ed, SE)
|
Assignee:
|
Valmet Paper Machinery, Inc. (Helsingfors, FI)
|
Appl. No.:
|
914199 |
Filed:
|
July 14, 1992 |
Foreign Application Priority Data
| Oct 25, 1988[SE] | 8803810.4 |
Current U.S. Class: |
162/290; 162/279; 162/301; 162/305; 162/359.1 |
Intern'l Class: |
D21F 009/00 |
Field of Search: |
162/113,116,206,359.1,279,290,301,360.3
|
References Cited
U.S. Patent Documents
3301746 | Jan., 1967 | Sanford et al. | 162/113.
|
3694311 | Sep., 1972 | Steppstedt | 162/359.
|
3891500 | Jun., 1975 | Kankaanpaa | 162/359.
|
4144124 | Mar., 1979 | Turunen et al. | 162/359.
|
4309246 | Jan., 1982 | Hulit et al. | 162/205.
|
4529480 | Jul., 1985 | Trokhan | 162/109.
|
4888096 | Dec., 1989 | Cowan et al. | 162/358.
|
Foreign Patent Documents |
2641714 | Jun., 1981 | DE.
| |
Primary Examiner: Hastings; Karen M.
Attorney, Agent or Firm: Bell, Seltzer, Park & Gibson
Parent Case Text
This application is a continuation of application Ser. No. 07/678,944,
filed on Apr. 16, 1991.
Claims
We claim:
1. A paper machine for manufacturing a soft crepe paper web, comprising a
headbox; a drying cylinder; a press roll cooperating with said drying
cylinder to define a nip through which the paper web passes; a forming
wire arranged to run in an extended endless loop from said headbox to said
press roll; an air and liquid permeable perforated belt arranged to run in
an endless loop passing around said press roll; a pick-up roll positioned
within the endless loop of said perforated belt to guide the belt into
contact with the forming wire at a location between said headbox and said
press roll so that the forming wire and the permeable belt continuously
sandwich the paper web therebetween along a distance from the pick-up roll
to the press roll; at least one suction means and at least one steam blow
nozzle, the suction means and steam blow nozzle being disposed opposite
each other on opposite sides of the paper web and cooperating with said
forming wire and said permeable belt in the region between said pick-up
roll and said press roll for directing jets of air through said forming
wire and said permeable belt and through the paper web sandwiched
therebetween to remove water from the paper web; a guide roll disposed
within the endless forming wire adjacent to the press roll and positioned
so that the forming wire and the permeable belt, with the paper web
sandwiched therebetween, wraps a predetermined sector of the press roll
before the forming wire separates from the paper web; suction means
disposed within said sector of said press roll to facilitate transfer of
the paper web to said belt, with the belt and the paper web carried
thereon thereafter passing through said nip, and cleaning means
cooperating with the loop of said permeable belt between said press roll
and said pick-up roll for cleaning the belt so that the permeability to
water and air is maintained.
2. A paper machine as claimed in claim 1 wherein said cleaning means
includes a water spray for washing the air and liquid permeable perforated
belt.
3. A paper machine as claimed in claim 2 wherein said water spray is
located inside the loop of said perforated belt, and including at least
suction box cooperating with the perforated belt downstream from the water
spray for removing water from the perforated belt.
4. A paper machine as claimed in claim 3 wherein the water spray is located
in a portion of the endless loop disposed above the paper web, and
including a trough for collecting water from the water spray.
5. A paper machine as claimed in claim 1 including at least one blow nozzle
directed toward the suction means in said press roll.
6. A paper machine for manufacturing a soft crepe paper web, comprising a
headbox; a drying cylinder; a press roll cooperating with said drying
cylinder to define a nip through which the paper web passes; a forming
wire arranged to run in an extended endless loop from said headbox to said
press roll; an air and liquid permeable perforated belt arranged to run in
an endless loop passing around said press roll; a pick-up roll positioned
within the endless loop of said perforated belt to guide the belt into
contact with the forming wire at a location between said headbox and said
press roll so that the forming wire and the permeable belt continuously
sandwich the paper web therebetween along a distance from the pick-up roll
to the press roll; a first suction box cooperating with said forming wire
at a location downstream from said pick-up roll, a second suction box and
a cooperating steam blow nozzle, said second suction box and steam blow
nozzle being disposed opposite each other on opposite sides of the paper
web and located downstream from said first suction box and cooperating
with said forming wire and said permeable belt for directing jets of air
through said forming wire and said permeable belt and through the paper
web sandwiched therebetween to remove water from the paper web; a guide
roll disposed within the endless forming wire adjacent to the press roll
and positioned so that the forming wire and the permeable belt, with the
paper web sandwiched therebetween, wraps a predetermined sector of the
press roll before the forming wire separates from the paper web; suction
means disposed within said sector of said press roll to facilitate
transfer of the paper web to said belt, with the belt and the paper web
carried thereon thereafter passing through said nip, and cleaning means
cooperating with the loop of said permeable belt between said press roll
and said pick-up roll for cleaning the belt so that the permeability to
water and air is maintained.
7. A paper machine as claimed in claim 6 including at least one additional
suction box cooperating with said forming wire between said headbox and
said pick-up roll.
8. A paper machine as claimed in claim 6 including at least one IR hood
disposed at the drying cylinder for heating the paper web on the drying
cylinder.
9. A paper machine as claimed in claim 6 including at least one IR hood
disposed for heating the paper web between the pick-up roll and the press
roll.
10. A paper machine for manufacturing a soft crepe paper web, comprising a
forming roll; a forming wire arranged to run in an extended endless loop
around said forming roll; an endless loop covering wire arranged to run
over the forming roll and said forming wire; a headbox arranged for
supplying stock between said forming wire and said covering wire; a press
roll located at a distance from said forming roll, said forming wire
extending from said forming roll to said press roll and arranged to pass
over said press roll; an air and liquid permeable perforated belt arranged
to run in an endless loop passing around said press roll; a pick-up roll
positioned within the endless loop of said perforated belt to guide the
belt into contact with the forming wire at a location between said headbox
and said press roll so that the forming wire and the permeable belt
continuously sandwich the paper web therebetween along a distance from the
pick-up roll to the press roll; a first suction box cooperating with said
forming wire at a location downstream from said pick-up roll; a plurality
of additional suction boxes located downstream from said first suction box
and cooperating with said forming wire and said permeable belt; a steam
blow nozzle cooperating with at least one of said additional suction boxes
and being disposed on the opposite side of the paper web from said
additional suction box for directing air through said forming wire and
said permeable belt and through the paper web sandwiched therebetween to
remove water from the paper web; a guide roll disposed within the endless
forming wire adjacent to the press roll and positioned so that the forming
wire and the permeable belt, with the paper web sandwiched therebetween,
wraps a predetermined sector of the press roll before the forming wire
separates from the paper web; a yankee drying cylinder disposed adjacent
said press roll and cooperating therewith to form a nip through which the
paper web passes for being transferred to the yankee cylinder; suction
means disposed within said sector of said press roll to facilitate
transfer of the paper web to said belt, with the belt and the paper web
carried thereon thereafter passing through said nip, and cleaning means
cooperating with the loop of said permeable belt between said press roll
and said pick-up roll for cleaning the belt so that the permeability to
water and air is maintained.
Description
The present invention relates to a paper machine for manufacturing a soft
crepe paper web, comprising a wet end having at least one forming wire for
forming and carrying a paper web, and a drying section provided with a
drying cylinder in which the paper web is dried, said paper machine having
a first operating arrangement for manufacturing a soft crepe paper web
with certain bulk and softness values, in which first operating
arrangement the drying section is provided with a felt movable in a loop
and arranged to run from a pick-up means at the transition between wet end
and drying section, to a press roll which defines a nip with the drying
cylinder, said felt carrying the paper web on its lower surface, and the
carrying forming wire being arranged to run up to said pick-up means in
the drying section to transfer the paper web formed to said felt.
The soft crepe paper web produced in a conventional paper machine of the
type described in the introduction, for instance, has certain upper
limited values for bulk and softness. To achieve bulk and/or softness
values above these limited values special methods have been utilized, such
as mixing in expendable microspheres of thermoplastic material as
described in U.S. Pat. No. 4,619,734, or utilizing machines which operate
with through drying see, for instance, U.S. Pat. No. 3,303,576, U.S. Pat.
No. 3,812,000, U.S Pat. No. 3,821,068 and U.S. Pat. No. 4,036,684 in which
the through drying is performed on cylinders with perforated outer
surface, which may be covered by a fabric for instance, hot drying air
being supplied internally and passing out through the cylindric surface,
or in the reverse direction.
U.S. Pat. No. 4,144,124 describes a twin wire machine for manufacturing a
soft crepe paper web wherein the carrying forming wire extends up to and
beyond a press roll from which the paper web is transferred to a yankee
cylinder, the press roll being wrapped by a loop of felt and possibly also
an embossing wire.
GB 602,237 relates to a fourdrinier machine for manufacturing a soft crepe
paper web wherein the formed paper web is transferred to a pick-up felt
running in a loop between the fourdrinier former and the roll which may
consist of a press roll pressing against a yankee cylinder, the under side
of the paper web carried by the pick-up felt being covered by a covering
felt running in a loop.
However, said twin wire machine and fourdrinier machine for manufacturing
soft crepe paper webs are so constructed that they cannot easily be
altered to different operating arrangements in order to produce soft crepe
paper webs of different qualities with respect to bulk and softness.
The object of the present invention is to eliminate the problem mentioned
above and to provide a paper machine for manufacturing a soft crepe paper
web which can easily be altered for adaptation to varying conditions on
the market, such as the competitive situation and to accommodate consumer
wishes.
The novelty of the invention lies substantially in that the paper machine
is rebuildable between said first operating arrangement and a second
operating arrangement for the production of a soft crepe paper web having
higher bulk and softness values in relation to the first operating
arrangement and in which second operating arrangement the carrying forming
wire is arranged to run in an extended loop from the wet end to the press
roll of the drying section, that the felt of the drying section is
replaced by a perforated belt of wire type, movable in a loop and
permeable to air and liquid, which is arranged to travel from said pick-up
means to said press roll in contact with the extended carrying forming
wire while enclosing the paper web therebetween in order to form a
continuous sandwich structure, that means producing jets of air are
arranged along the sandwich structure to remove water from the paper web
by means of air flowing through the paper web, and that cleaning means are
arranged along the loop of the belt to clean it so that the permeability
to water and air is maintained.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described further in the following with reference to
the drawings, in which
FIG. 1 shows schematically a paper machine for manufacturing a soft crepe
paper web in a first conventional operating arrangement.
FIG. 2 shows schematically the paper machine according to FIG. 1 in a
second, rebuilt operating arrangement in accordance with the present
invention.
FIG. 3 is a diagram showing the relation between drying strength and
softness for soft crepe paper webs produced according to the two different
operating arrangements.
DETAILED DESCRIPTION
With reference to FIG. 1, it is schematically shown therein parts of a
conventional paper machine suitable for the manufacture of a soft crepe
paper web such as tissue and other sanitary paper products. The paper
machine shown is a twin wire machine comprising a wet end 1 and a dry
section 2. The wet end includes a headbox 3, a movable carrying forming
wire 4, a movable covering forming wire 5 and a forming roll 6 which may
be perforated and provided with suction means. Alternatively, the forming
roll may be smooth. The headbox 3 supplies a single or multi-layer flow of
stock between the two moving forming wires 4, 5 for forming a paper web 7
by dewatering the stock. The two forming wires 4, 5 run together over the
forming roll 6 and then in individual loops over a plurality of rolls
arranged to impel, guide, align and stretch the carrying forming wire 4
and the covering forming wire 5. The rolls defining the path of the
covering forming wire 5 include a breast roll 8 and, a short way after the
forming roll 6, a guide roll 9 which can be termed a forward drive roll.
The covering forming wire 5 leaves the carrying forming wire 4 and the
paper web 7 either immediately before the wire 4 and paper web 7 diverge
from the forming roll 6, or at a transfer suction box, not shown, or other
transfer means located between forming roll 6 and forward drive roll 9.
The carrying forming wire 4 runs to the drying section 2 where it leaves
the paper web 7 by changing its direction of travel around a guide roll
11.
The drying section 2 comprises a drying cylinder 12 having relatively large
diameter and a polished cylindric surface. The drying cylinder 12,
preferably consisting of a yankee cylinder, is covered by a hood (not
shown), in which hot air is blown at high speed against the paper web 7.
The paper web is creped from the yankee cylinder 12 by means of a creping
doctor (not shown) to obtain the desired creping, after which the finished
creped paper web is wound onto a roll. Further, the drying section 2
includes a felt 13 disposed upstream of the yankee cylinder 12 and
travelling in a loop around several rolls and around a pick-up means,
suitably in the form of a roll 14, located nearest the wet end 1 and
thereby in the vicinity of said guide roll 11 for the carrying forming
wire 4, and a press roll 15 which presses against the yankee cylinder 12
and is provided with suction means 16 to dewater the paper web before the
latter comes into contact with the yankee cylinder 12. The pick-up means
may alternatively consist of a shoe. Further, two guide rolls 17, 18 are
disposed between the pick-up roll 14 and press roll 15, said guide rolls
17, 18 deflecting with a small angle the direction of travel of the felt
13. A blind-drilled roll 19 is disposed after the press roll 15, in
contact with the yankee cylinder. The paper web 7 is transferred to the
felt 13 at the point where this and the carrying forming wire 4 converge
at the pick-up roll 14 and thereafter immediately diverge from each other.
Suitable conditioning means (not shown) are disposed along the loop of the
felt 13 in order to condition the felt prior to contact with the paper
web.
FIG. 2 shows schematically the same paper machine as that according to FIG.
1 with respect to its basic structure, but supplemented and modified in
accordance with the present invention, enabling it to be rebuilt between a
first operating arrangement according to FIG. 1 and a second operating
arrangement according to FIG. 2. Modification to the second operating
arrangement substantially consists of removing the felt 13 and replacing
it with an endless, perforated belt 25 of wire type, permeable to air and
liquid, and of extending the carrying forming wire 4a up to the yankee
cylinder 12 to that it travels in a larger loop with respect to said first
operating arrangement and over a predetermined sector of the press roll
15. The carrying forming wire 4a travels in contact with the belt 25 from
the pick-up roll 14 to the press roll 15, encasing the paper web 7 between
itself and the belt 25 as an intermediate layer for forming a continuous
sandwich structure that is maintained up to the press roll 15.
A guide roll 26 is disposed in the larger loop of the carrying forming wire
4a, after and spaced from the point where the belt 25 first encounters the
press roll 15, so that the carrying forming wire 4a travels around said
predetermined sector of the press roll 15, this being sufficient for the
paper web to be transferred to the belt with the aid of suction means 16
inside the press roll 15, said suction means being disposed within said
sector and up to the nip defined by the press roll 15 and yankee cylinder
12. Further, additional rolls 27 are disposed within and outside the
larger loop of the carrying forming wire 4a in order to guide and stretch
it. The previously mentioned guide roll 11 is not used in this modified
second operating arrangement.
No extra rolls are required for installation of the belt 25. Instead, the
loop can be made shorter in relation to the felt 13 used previously, since
the roll 19 is superfluous, and thus also the two guide rolls 20, 21 in
the vicinity thereof.
Suction boxes 28 may be mounted before the guide roll 14 where the paper
web 7 thus is exposed. (Such suction boxes may also be used in the first
operating arrangement.) The paper web can hence be dewatered to a dry
solids content of up to a maximum of 25%. By extending the carrying
forming wire 4a as described, and allowing this to cooperate with an open
belt 25 of wire type, which has equal or substantially equal permeability
to water and air as the forming wire 4a, in order to encase the paper web
therebetween to form a continuous sandwich structure as described, it is
not possible to arrange additional dewatering means producing jets of air,
along this sandwich structure in order to further increase the dry solids
content before the yankee cylinder. In the modified operating arrangement
of the paper machine shown in FIG. 2 these means comprise a suction box 29
disposed on the under side of the sandwich structure immediately after the
guide roll 14, and a pair of suction boxes 30, 31 disposed on the upper
side of the sandwich structure downstream of the lower suction box 29, a
steam blowing tube 32 being disposed on the other side of the sandwich
structure, opposite the suction box 30. Further, a blowing nozzle 44 may
be disposed at the press roll 15 in the loop for the forming wire 4a,
opposite said sector of the press roll 15 where a part of the suction
means 16 is thus located. Moreover, cleaning means are also disposed at
one or more points between the press roll 15 and the pick-up roll 14, seen
in the direction of movement of the belt, to clean thoroughly the belt to
ensure that its permeability to water and air is continuously maintained.
In the embodiment shown these cleaning means comprise a water spray tube
33 disposed inside the loop and two suction boxes 34, 35 and an
oscillating high pressure spray tube 36 disposed between the suction boxes
outside the loop, immediately downstream of said water spray tube 33.
Further, a water spray tube 38 is provided at the nip defined by the open
belt 25 and the roll 37 located after the suction boxes 34, 35, said spray
tube 38 supplying water to produce a liquid film between the roll and
belt. A pipe 39 for blowing air is disposed outside the loop, immediately
before the last roll 40, before the belt 25 reaches the guide roll 14. The
water from the water spray tubes 33 and 38 is collected in a trough 41.
The drying section 2 may also include means for IR heating of the paper web
7. An IR hood 45 may be disposed, for instance, at a point on the yankee
cylinder 12 where the paper web is exposed between press roll 15 and said
drying hood covering the yankee cylinder 12. One or more IR hoods 46 may
also be disposed between the pick-up roll 14 and the press roll 15 to IR
heat the paper web while this forms the intermediate layer of the sandwich
structure.
In its second operating arrangement according to FIG. 2, the paper machine
may be provided with a press felt (not shown) moving in a loop, said press
felt being arranged inside the loop of belt 25 or the carrying forming
wire 4a, running around a press roll, not shown, pressing against one side
of the sandwich structure and an opposite press roll, not shown, which may
also be wrapped by such an inner press felt. If desired such an inner
press loop, arranged inside the loop of the belt 25 may be extended to
also run around the press roll 15.
Since the belt 25 is perforated or open, i.e. provided with a great number
of through-holes running in the thickness direction of the paper web 7, it
will function as an embossing belt so that when the paper web 7 passes the
nip between press roll 15 and yankee cylinder 12, parts of it will be
pressed into these holes, thus producing a relief pattern. These parts of
the paper web pressed into the holes will not be subjected to any
appreciable pressure, thus contributing to higher bulk and softness.
The paper machine described can easily be changed to the different
operating arrangements in order to manufacture soft crepe paper webs of
different qualities with respect to bulk and softness, in dependence of
the varying conditions prevailing on the market at the moment. These
conditions may quickly change from one time to another. Furthermore, the
extra drying devices placed within the range of the sandwich structure in
the second operating arrangement, enable increased dry solids content to
be achieved before the yankee cylinder so that the paper machine can be
run at increased speed which is at least substantially equivalent to the
speed of through drying machines mentioned in the introduction.
FIG. 3 illustrates the relation between dry strength and softness. The line
A indicates average values for soft crepe paper web produced using the
conventional first arrangement of the paper machine. It is clear that a
desired increased strength results in reduced softness. Conversely a
desired increased softness results in reduced strength of the soft crepe
paper web. Line B indicates average values for soft crepe paper web
produced using the second operating arrangement of the paper machine
according to the present invention. Thus, it is clear that within a
desired range for the strength of the soft crepe paper web, higher
softness is obtained in relation to soft crepe paper web produced using
the paper machine in its conventional arrangement.
The invention has been described in connection with a twin wire machine,
however, it can also be applied to a fourdrinier machine in which the
supporting forming wire, i.e. the fourdrinier wire, is extended up to the
yankee cylinder in the same way as the carrying forming wire 4a in the
twin wire machine described.
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